1. Field of the Invention
The present invention relates to a multi-band multi-layered chip antenna, which can be mounted in GSM (Global System for Mobile communication), DCS (Digital Europe Cordless Telephone) and BT (Bluetooth) terminals, and particularly to a multi-band multi-layered chip antenna using double coupling feeding, which realizes multi-band characteristics using a feeding radiation element and double parasitic radiation elements in the chop antenna, so that with impedance adjustment between the double parasitic elements, control of frequency and bandwidth, enhancement of impedance characteristics and radiation efficiency, and minimized influence of mutual impedance between the radiation elements can be realized.
2. Description of the Related Art
In general, as for an antenna applicable to mobile communication terminals, such as GSM, DCS, BT and the like, a helical antenna formed as an outward protrusion on the communication terminal or a linear monopole antenna retractable into the communication terminal are mainly used. Although such a helical antenna or a monopole antenna has an advantage of a non-directional radiation characteristic, since these antennas are an external type in which the antenna is protruded outward from the terminal, there are worries about damage of an appearance due to an external force, leading to deterioration of the characteristics, and these antennas have a low Specific Absorption Rate (SAR), which has been proposed recently.
Meanwhile, recent requirements of the mobile communication terminals are miniaturization, lightweight and multi-functionality. In order to satisfy these requirements, built-in circuits and components to be employed in the communication terminal also have tendencies toward the miniaturization as well as the multi-functionality. These tendencies of miniaturization and multi-functionality are also required of the antenna, one of the most important components of the communication terminal.
As for conventional built-in type antennas, there are micro-strip patch antennas, planar inverted F-type antennas, chip antennas, and the like. There are suggested methods of effectively miniaturizing these built-in type antennas. For instance, there is a method by which the micro-strip patch antenna having a relatively high gain and wide bandwidth characteristics is reduced in size using an aperture coupled feeding structure. According to this method, with an electric field distribution of TM01 mode of the micro-strip patch antenna, the dielectrics are inserted in the longitudinal direction of a resonance patch to a lower portion of an edge of the patch where the electric field distribution is highest, effectively reducing the size of the antenna and minimizing gain reduction in the antenna, which can occur due to an increase of the dielectric constant, thereby providing a lightweight, miniaturized antenna.
However, since the method of miniaturizing the currently available antenna is based on a planar structure, there is a limitation in miniaturization, and when considering the current tendency of reducing space for the antenna to be mounted in a PDA (Personal Digital Assistant) caused by an increase in service of the PDA, there is a need to provide an enhanced method.
Further, although inverse L-type, inverse F-type and the like are used as feeding type antennas used in the conventional antennas, there is a need to enhance the feeding type in view of space efficiency.
FIG. 1 is a perspective view illustrating the structure of a conventional multi-layered chip antenna.
The conventional multi-layered chip antenna shown in FIG. 1 is an antenna miniaturized such that the antenna can be used in the multi-band, in which first and second radiation patches 30 and 40 of the antenna are coupled to each other via a feeding part 20 at an upper portion of one edge of a ground metal plate 10, and the feeding part 20 is coupled to the ground metal plate 10 in the perpendicular direction.
The first radiation patch 30 defining the top surface of the antenna has a labyrinth-shaped fold slit patch structure, and is parallel to the planar upper surface of the ground metal plate 10.
The second radiation patch 40 is positioned between the first radiation patch 30 and the ground metal plate 10 while being parallel to the first radiation patch 30 and the ground metal plate 10. The secondary radiation patch 40 comprises a plurality of strip patches 41 and 43 having lengths and widths different from each other, respectively, and each of the strip patches 41 and 44 can be positioned on an identical plane, or can be laminated with each other.
The feeding part 20 comprises a feeding pattern 21, a feeding pattern extension 22, a feeding pattern ground portion 23, and the like. The feeding pattern 21 acts to transmit signals between a body of the PDA and the first and second radiation patches 30 and 40 of the antenna, and is perpendicularly coupled to a feeding metal conductor provided at one side of the ground metal plate 10. The feeding pattern extension 22 extends perpendicular to the feeding pattern 21 from a predetermined portion of the feeding pattern 21, and the length of the feeding pattern extension 21 can be varied. The feeding pattern extension 22 is bent toward the ground metal plate 10 at the end of the feeding pattern extension 22, grounded to the ground metal plate 10.
Meanwhile, although the conventional multi-layered chip antenna can be available in multi-band and have a miniaturized structure, there are problems as follows.
First, since the first radiation patch 30 constituting the antenna has patterns, almost all of which are formed on one plane, and the second radiation patch 40 has the other patterns, almost all of which are formed on the other plane, there is a problem in that the miniaturization of the antenna is limited.
Further, since both patterns of the first and second radiation patches 30 and 40 constituting the antenna respectively have shapes of a substantially straight line, there is a problem in that the miniaturization of the antenna is limited.
Additionally, since both the first and second radiation patches are directly coupled to the feeding line, if there is a need to adjust a frequency due to a process variation after manufacturing the antenna according to a predetermined design, change of one patch has a direct influence on the other patch connected to the patch, thereby making frequency operation difficult.